The handling of fine particulate, particularly that of low density and low specific gravity, has always been troublesome at best and hazardous at worst. A continuing difficulty has resulted in the handling of the ten to twenty micron diameter toner particulate used in xerographic copying machines. This carbon black based toner is not easily poured and when agitated "clouds" and dusts all over the machine and the operator attempting to fill the machine. The air-borne toner fouls the lenses and mirrors of the copying machine thus increasing the amount of service calls required for the machine thus resulting in customer disatisfaction. The well and dispensing mechanism in many xerographic copying machines presently in use is described in a number of U.S. patents, including U.S. Pat. No. 3,692,403 of Sept. 19, 1972 to Turner, U.S. Pat. No. 3,062,109 of Nov. 6, 1962 to Mayo, et al, and U.S. Pat. No. 3,013,703 of Dec. 19, 1961 to Hunt. This type of dispenser is charged by pouring the toner particulate from a bottle into the well from which it is dispensed by the reciprocal motion of an open grate located at the base of the well.
In addition to the well known difficulties in filling the well from a bottle, the dispensing rate of these machines using the well and grate is not constant causing a continual change of lightness to darkness to lightness. As the dispensing rate diminishes, there is less toner available to the copying apparatus and the prints become lighter and of poorer quality. If the operating instructions are followed, the toner well is stirred thus dispensing the toner at a grossly faster rate for a short period of time. This provides darker printing but also darkens the background thus reducing the contrast. What is needed is a controlled rate of toner flow to provide a balance between the amount of toner needed for darkness of print and lightness of background. This need for better control of dispensing rate is particularly noticeable on long runs of copying the same original. Other remedies have been recommended such as knocking the toner well but these remedies tend to increase the amount of toner in the machine thus darkening the copies for a time, but do not provide a controlled dispensing rate.
Later xerographic machines have been designed with dispensers which eliminate the need for hand pouring of the toner powder. These dispensers utilize a cartridge having a resilient open-called elastomeric roller dispenser utilizing rotational force. This type of apparatus is described in U.S. Pat. No. 3,596,807 of Aug. 3, 1971 to Hudson, et al, U.S. Pat. No. 3,608,792 on Sept. 28, 1971 to Hudson, and U.S. Pat. No. 3,678,897 on July 25, 1972 to Hewitt. While these machines eliminate the necessity of pouring the toner from a bottle, the other short comings of xerographic machines are still present. In addition, there are literally hundreds of thousands of xerographic copying machines presently being used that cannot utilize this later development with the elastomeric roller dispenser.
It is therefore, a primary object of this invention to provide a dispenser for fine particulate.
In addition, it is an object to provide an apparatus for holding and dispensing toner particulate. An object of this invention is to provide a dispenser which yields a continuous controlled feed of fine toner particulate to a xerographic machine so as to prevent large changes in the darkness of copy obtained.
Another object of this invention is to provide a dispensing cartridge which can be placed directly into xerographic and other dry copying apparatus without the necessity of the operator having to handle the toner in any way, thus, preventing clouding, spillage and contamination of the machine or the surrounding area.
An additional object is to provide a toner dispenser which essentially eliminates the problems caused by bridging of the toner particulate which are only partially solved presently by knocking the toner reservoir, stirring the reservoir, and the like.
A particular object of this invention is to provide a toner dispenser with a fine control of dispensing rate such that the particulate is introduced into the copying machine at a controlled rate so as to improve the consistency of the darkness of the copies, particularly over a long run using the same or similar originals.